1. Field of Invention
This invention relates to shipping baskets and casks for storing and transporting spent nuclear waste materials, and particularly to multi-purpose baskets and casks for transporting, storing, and disposal of pressurized water reactor (PWR) plants waste spent fuel and other waste materials.
2. Description of the Related Art
Various baskets and casks have been proposed and implemented for transporting, storing, and disposal of nuclear waste material. However, previous baskets and casks have been limited by durability, cost, and failure to meet stringent regulatory criteria. The present invention overcomes all such limitations by providing a multi-purpose basket which is a separate component of and not integral with a cask which is typically used to encompasses a fuel basket.
A nuclear reactor operates by initiating, maintaining and controlling fission chain reactions. These reactions occur within fissionable material such as Uranium 235 placed within the core of the reactor. In commercial type reactors, nuclear fuel is most often configured in the form of fuel assemblies, which are approximately 12-15 feet long and have a square cross section. Nuclear fuel is both loaded into and removed from the nuclear reactor one assembly at a time.
Since the nuclear reactor operates generating fission chain reactions, the nuclear fuel within a fuel assembly gradually becomes depleted and fission product contaminants build up until it reaches the point that it is no longer capable of maintaining the chain reactions necessary for operation of the reactor. When this occurs, the fuel assembly is removed from the reactor and replaced by a new fuel assembly. The depleted or spent fuel assembly, although incapable of maintaining the fission chain reaction in the reactor, is still highly radioactive and generates a significant amount of heat. Typically, a spent fuel assembly is stored in a pool of water called a spent fuel pool for a period of time after it is removed from the reactor, until temperatures and radioactivity levels have decreased enough to make it safe to move to another form of storage, or transport to a facility for reprocessing or disposal of the spent material.
After a spent fuel assembly has cooled sufficiently to permit its transfer, one of several alternative events may occur. The fuel assembly may be packaged and moved to another location on the reactor site for interim storage, or it may be packaged and transported to a remote site, sometimes at a long distance from the reactor site, for reprocessing, storage, or disposal.
One type of nuclear power plant is a plant which uses two separate systems, completely isolated from one another, to produce power. The primary system circulates water through the reactor core and through a heat exchanger, which is used to transfer heat to the secondary system. Water in the primary system is kept at a high pressure which allows the water to achieve a high temperature without boiling. The heat transferred to the secondary system is used to produce steam which drives a turbine generator to produce electricity. This type of plant is referred to as a pressurized water reactor (PWR) plant. The fuel assemblies used within PWR reactors have characteristics such as size and composition that make them unique with respect to fuel assemblies from other types of nuclear reactors.
Although prior baskets and containers have been proposed and developed to store or transport nuclear fuels all suffer significant limitations and disadvantages. For example, U.S. Pat. No. 4,827,139 issued to Wells et al. discloses a cylindrical cask which contains a fuel basket composed of independent tubes. Such basket is integral with the cask, i.e. the basket is not a separate component, it is not separately sealed, and it cannot be removed from the cask after fuel has been loaded into it. The basket of Wells et al., for example, is capable of containing 31 fuel assembles of an unnamed type, while the basket of the present invention may hold 24 PWR reactor fuel assemblies. Moreover, the present invention comprises a multi-purpose basket which is a separate component not integral with a cask. After fuel assemblies have been loaded into the basket of the present invention, the basket is sealed and may be placed within and removed from various types of casks, such as storage casks, transportation casks, or transfer casks, thereby enabling the basket to be used for many different applications.
While other baskets have been proposed and configured to act as a separate and removable component of casks all differ significantly from the present invention by using a different basket structure than the sleeve and internal support structure disclosed herein and are restricted to accommodating fewer fuel assemblies.
The present invention encompasses a multi-purpose, sealed, fuel basket which secures and contains PWR water reactor type fuel assemblies. The basket of the present invention may be used for various applications including:
1. Storage of contained fuel assemblies inside of a storage cask for storage either at the reactor site of at a remote site. PA1 2. Transporting of contained fuel assemblies from one location to another inside a transportation cask over public or private transportation routes. PA1 4. Disposal means for the disposal of spent nuclear fuel used in a facility or facilities constructed for the disposal of spent nuclear fuel.
3. Transfer means for transferring the contained fuel assemblies inside of a transfer cask between the spent fuel pool, a storage cask, and a transportation cask.
The basket of the present invention provides a means to meet the very stringent set of criteria that has been established by regulatory authorities in order to ensure safety during the transportation and storage of nuclear fuel assemblies. The basket is specifically designed and constructed to ensure that the nuclear chain reaction is maintained below critical limits, and harmful radiation does not escape. The basket configuration assures that these conditions are maintained even under extreme circumstances such as accidents, geologic stress, pressure, and the like.
Accordingly, it is the primary object of this invention to provide a basket for the containment of nuclear waste from nuclear reactors which is extremely durable, resilient, easy to use, store, transport, and contain, and which is adaptable to a wide variety of storage casks, transportation casks, transfer casks, and contained fuel assemblies.
Additional objects and advantages of the invention will be set forth in the description which follows, and in part will be obvious from the description, or may be learned by practice of the invention. The objects and advantages of the invention may be realized and obtained by means of the instrumentality's and combinations particularly pointed out in the appended claims.